1. Field of the Invention
The present invention relates to a framework for 3D non-photorealistic rendering and a method of configuring the framework, and more particularly, to a framework that renders a 3D model in a general and intuitive manner like the way an artist selects a style and paints a model with the selected style and has a flexible style expandability for efficient non-photorealistic rendering by using a unified concept of expressing various rendering styles using just two rendering methods (face painting and line drawing), and a method of configuring the framework.
2. Description of the Related Art
With the increasing interest in non-photorealistic rendering and animation, a number of researches have been conducted to generate images in an artistic style that look like a painting or drawing. Early researches are focused on developing non-photorealistic rendering and animation systems that are individually dedicated to expressing a particular rendering style. Such systems use a non-photorealistic rendering pipeline that is obtained by slightly modifying a traditional rendering pipeline.
Recently, unified frameworks have been researched to establish such an individual non-photorealistic rendering pipeline and provide a non-photorealistic rendering that is different from the existing photorealistic rendering. In a framework for non-photorealistic rendering based on a particle (1996), a particle is used to determine the position of a stroke (denoting a brush touch). The particle-based framework is the earliest framework that is still in use. Further, examples of recently proposed frameworks include a framework that expresses a 3D model using an adaptively sampled distance field (ADF) (an article titled “A New Framework for Non-photorealistic rendering”, 2001) and a framework based on a graphic processing unit (GPU). However, in the above-described frameworks, main concerns of non-photorealistic rendering systems (i.e., processing techniques for expressing styles) are not mentioned.
A framework somewhat different from the above-described frameworks is disclosed in “OpenNPAR (2003, an article titled ‘OpenNPAR: A system for developing, programming, and designing non-photorealistic animation and rendering’).” This OpenNPAR system is an OpenInventor-based framework, in which each rendering style for expressing a non-photorealistic effect is matched with a combination of components and a desired style is generated by recombining the components. Although the OpenNPAR system modularizes detail non-photorealistic rendering styles (detail functions) and expresses a number of styles by recombining the modularized styles, the OpenNPAR system has a complicated basic concept in intuitive and non-photorealistic expressing. Further, the OpenNPAR system has a complicated basic pipeline that supports a developer (develops modules), a programmer (produces modifiers using the modules), a designer (generates styles using the modifiers), and a user.